/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.server.handler;

import java.util.Arrays;
import java.util.Collections;
import java.util.List;

import reactor.core.publisher.Mono;

import org.springframework.util.Assert;
import org.springframework.util.ObjectUtils;
import org.springframework.web.server.ServerWebExchange;
import org.springframework.web.server.WebFilter;
import org.springframework.web.server.WebFilterChain;
import org.springframework.web.server.WebHandler;

/**
 * Default implementation of {@link WebFilterChain}.
 *
 * @author Rossen Stoyanchev
 * @since 5.0
 */
public class DefaultWebFilterChain implements WebFilterChain {

    private final List<WebFilter> filters;

    private final WebHandler handler;

    private final int index;


    public DefaultWebFilterChain(WebHandler handler, WebFilter... filters) {
        Assert.notNull(handler, "WebHandler is required");
        this.filters = ObjectUtils.isEmpty(filters) ? Collections.emptyList() : Arrays.asList(filters);
        this.handler = handler;
        this.index = 0;
    }

    private DefaultWebFilterChain(DefaultWebFilterChain parent, int index) {
        this.filters = parent.getFilters();
        this.handler = parent.getHandler();
        this.index = index;
    }


    public List<WebFilter> getFilters() {
        return this.filters;
    }

    public WebHandler getHandler() {
        return this.handler;
    }


    @Override
    public Mono<Void> filter(ServerWebExchange exchange) {
        return Mono.defer(() -> {
            if (this.index < this.filters.size()) {
                WebFilter filter = this.filters.get(this.index);
                WebFilterChain chain = new DefaultWebFilterChain(this, this.index + 1);
                return filter.filter(exchange, chain);
            } else {
                return this.handler.handle(exchange);
            }
        });
    }

}
